The present invention relates to a plasma addressed liquid crystal display (LCD) and the manufacturing method thereof, and more particularly to a plasma addressed LCD having an improved plasma addressing unit and its manufacturing method.
Various types of displays include a phosphor display tube using a low-speed electron beam, a plasma display using gas discharge, an electroluminescence (EL) display using the electro-luminescence effect, an electro-optical liquid crystal display (LCD), as well as a traditional cathode ray tube using a high-speed electron beam. These various displays are selectively adapted according to their characteristics since they have different functions and structures. Their common purpose is to visualize an electrical image or data signal. The displays have been developed structurally and functionally in their respective fields.
Recently, a matrix-type display compositely constructed with the plasma discharge device and electro-optical device, that is, an LCD is disclosed in U.S. Pat. No. 4,896,149 by Tektronix.
The display is to address individual line by way of a plasma discharge which is shown in FIG. 1. Referring to FIG. 1, the display is constructed such that a liquid crystal shutter 10 in which a plurality of striped data electrodes 14 are arranged in parallel, is overlapped with a plasma addressing unit 20 in which a plurality of scanning lines 21 are arranged at right angles to striped data electrodes 14 of liquid crystal shutter 10. A background light generator 30 usually formed with an EL display is provided to the rear of the plasma addressing unit.
Referring to FIG. 2, liquid crystal shutter 10 has first and second transparent substrates 12 and 13 between which liquid crystal 16 is filled. Striped data electrodes 14 are formed on the inner side of first substrate 12. Among these two substrates, second substrate 13 has a relatively thin thickness of 50.mu.m and plays an important role in the orientation of liquid crystal. Plasma addressing unit 20 has a plurality of grooves 24 which form scanning lines 21 on a third substrate 25 perpendicular to the striped data electrodes. A pair of electrodes 22 and 23 are provided in parallel on either side of the bottom of each groove 24. In this configuration, third substrate 25 is adhesively fixed with second substrate 13 of liquid crystal shutter 10 so that grooves 24 form a closed discharge space in which discharge gas is filled.
In liquid crystal shutter 10, since a data signal is applied to a selected data electrode 14, a potential for activating the liquid crystal is formed along a selected data electrode 14. In plasma addressing unit 20, according to the ionized state of each discharge line due to the plasma discharge of each sequentially-selected plasma scanning line 21, a positive potential for activating the liquid crystal 16 is formed linearly along scanning line 21 on second substrate 13 in contact with the liquid crystal. Accordingly, a potential difference is formed by a selected data electrode 14 of liquid crystal shutter 10 and scanning line 21 of plasma addressing unit 20. Liquid crystal positioned at the intersection is activated and oriented by the potential difference at the interconnection, which forms a light passing dotted area through which light from the rear ward back light generator passes.
In other words, in plasma addressing unit 20, when voltage of a predetermined potential is applied to a pair of parallel electrodes 22 and 23 on a sequentially selected scanning line, linear direct-current-discharge occurs between parallel electrodes 22 and 23. Due to this, a linear potential is formed along scanning line 21 on the thinner second substrate 13. When the linear potential is formed on second substrate 13 by the linear discharge on scanning line 21 selected by the scanning signal, a data signal is selectively applied to data electrode 14 of the upper liquid crystal shutter 10. When liquid crystal is then activated by the potential difference at the intersection of the selected data electrode 14 and the selected and discharged scanning line 21 and is locally re-arranged, back light passes, forming one picture point.
The display is a unique flat-panel display which orients the liquid crystal by the data electrodes and scanning lines. Its drawback is that as described above, since the addressing unit requires, as its structural base, grooves 24 formed on the third substrate and a pair of electrodes 12 and 13 formed on the bottom of third substrate 25, the manufacture of the display is very elaborate. In other words, to form grooves 24 on third substrate 25, complicated etching process is required. Especially, forming a pair of electrodes on the bottom of each groove requires more than a simple silk screen printing method; a photolithography method including a metal deposition is needed. Such a technique to form a groove on glass, followed by an electrode formed thereon, is very complicated, especially for a large-screen display.